1. Field of the Invention
The present invention relates to a multiphase pumping system with a recycling loop.
The pumping system according to the invention is suitable for carrying, via pipes, a fluid comprised of at least one liquid phase and at least one gaseous phase, whose gas phase to liquid phase volumetric ratio (generally designated GLR) can vary widely.
Such a pumping system has applications particularly in the field of oil production for transporting, to a given destination point, petroleum effluents from an underground deposit, and particularly for working offshore deposits.
2. Description of the Prior Art
Existing multiphase pumping systems have a multiphase pump such as for example that described in U.S. Pat. No. 5,375,296 filed by the Assignee capable of applying a high pressure to a multiphase fluid provided the GLR volume ratio does not exceed a certain maximum value. When the GLR of the fluid to be transported exceeds this maximum value, as occurs in oil production when the fluid produced by a producing well has air pockets or plugs, a regulator is associated with the pump. These regulators are designed to limit the possible range of variation of the GLR to make it compatible with that accepted by the pump.
A known regulator, as described for example in U.S. Pat. No. 5,393,202 has for example a buffer tank receiving fluids produced by the deposit and having one or more perforated sampling tubes capable of automatically adjusting the phase ratio admitted at the pump inlet.
Such an arrangement gives satisfactory results but has the drawback of being bulky and relatively expensive.
U.S. Pat. No. 4,894,069 teaches a pumping system with a regulating loop. The pump outlet is connected to a phase separation device designed to extract multiphase fluid having a fraction composed almost completely of liquid. This liquid fraction is recycled by a branch line to the pump inlet where it reduces the value of the GLR ratio when it becomes excessive.